Donor apparatus

ABSTRACT

A developing system for latent images wherein a rotating fur brush receives marking particles from a donor assembly comprising a plurality of discrete elongated donor members which are successively moved through a closed path defining a volume within a sump housing, a portion of the defined volume being occupied by marking particles contained in the housing. The donor members may be circular, crescentic, or other configurational cross-sections and may or may not cooperate with a doctor blade. They may be in the form of taut flexible elements which are vibrated slightly to remove excessive toner. In certain embodiments, a striking element in the form of a thin taut but flexible wire or other material is used to charge and fluff the fibrous applicator as well as redistribute undesirable concentrations of toner within the applicator.

United States atent [191 Stange DONOR APPARATUS [75] Inventor: Klaus K. Stange, Pittsford, NY.

[73] Assignee: Xerox Corporation, Rochester, NY. [22] Filed: May 10, 1972 [21] Appl. No.: 251,954

Related US. Application Data [60] Division of Ser. No. 864,265, Sept. 24, 1969, Pat. No. 3,687,106, Continuation-in-part of Ser. No. 840,967, July 11, 1969, abandoned.

[52] U.S. Cl. 118/637, 117/175 [51] Int. Cl 603g 13/00 [58] Field of Search 96/1 A; 117/175; 118/621,

[ Nov. 19, 1974 Primary Examiner-W. C. Reynolds Assistant Examiner-Leo Millstein 57 ABSTRACT A developing system for latent images wherein a rotating fur brush receives marking particles from a donor assembly comprising a plurality of discrete elongated donor members which are successively moved through a closed path defining a volume within a sump housing, a portion of the defined volume being occupied by marking particles contained in the housing. The donor members may be circular, crescentic, or other configurational cross-sections and may or may not cooperate with a doctor blade. They may be in the form of taut flexible elements which are vibrated slightly to remove excessive toner. In certain embodiments, a striking element in the form of a thin taut but flexible wire or other material is used to charge and fluff the fibrous applicator as well as redistrig te un de ir ab1e concentrations of toner within the applicator.

5 Claims, 10 Drawing Figures PATENIEL NEW 1 91974 SHEET 10F 4 F/GZ PI'UENTEL SHEET 2 g; 4 3,848,566

PATENIE szuv 1 9mm saw any 4 3.848.566

FIG. 7

DONOR APPARATUS This is a division, of application Ser. No. 864,265, filed Sept. 24, 1969, now U.S. Pat. No. 3,687,106.

This is a continuation-in-part of application Ser. No. 840,967 filed July 11, 1969 now abandoned, assigned to the same assignee as the instant application.

This invention relates generally to donor assemblies, for making marking particles available to a developing applicator in apparatus wherein a latent image, either electrostatic or magnetic, is to be developed with such particles.

In conventional developing systems, a rotating cylindrical natural fur brush has sometimes been used to convey marking particles, or toner, into transfer relation with a latent image to be developed.

In the past, toner has been sprinkled or blown onto the brush, as well as brought into contact with the brush via a donor assembly in the form of a solid cylindrical roller which rotates in a sump of developer, i.e., toner and carrier bead mixture.

However, these approaches have suffered severe limitations and disadvantages which directly affect the quality and consistency of the development of latent images.

One disadvantage is the effect of pumping or the uniform and constant movement of the developer in one direction as the roller moves through the sump. As the body of the roller moves it pushes developer before it and soon forms a cavity in the quantity of developer in the sump. Additionally, when prior art systems were inactive for long periods or in storage the developer mixture would cake and compact thereby making good development impossible without stirring the mixture prior to operation. Such conditions were alleviated by additional apparatus such as complicated vibrators or agitators which attempt to cause the developer to break up or fall into this cavity to the extent that the donor assembly will allow. While augmenting the total cost complexity and size of the development system, these remedies are partial at best in their success.

Another solution is to use a large amount of carrier beads in the developer mixture to lend more fluidity to the toner or pigmented marking particles. In this way, the developer mixture will more readily seek its own level in the sump. However, such large concentrations of carrier beads consume precious space in the developer assembly which could better be occupied by toner thereby shortening the interval between service calls or operator intervention to replenish the toner supply.

Many times such prior art apparatus cannot present to the donor assembly a constant amount of developer since this amount is a function of the varying level of developer in the sump. Furthermore, in many instances a certain residual amount of developer remains unused in the sump since it cannot be placed within the effective reach of the donor assembly.

The prior art use of natural or synthetic fibrous applicators for developing latent electrostatic charge patterns in conjunction with a solid cylindrical donor roller encounters additional difficulties. The contact between the applicator and the recording surface to be developed as well as the contact with the donor roller have the undesirable effect of compacting the fibers of the applicator. This results in a degradation of the developed image. To restore the fluff of the applicator to a degree required for good development, a striker plate or comb structure has been suggested by the prior art such as US. Pat. No. 3,251,706 to L. E. Walkup. However, these structures are believed to have drawbacks such as complex mounting arrangements and excessive toner buildup on the structure itself.

In addition, to the disadvantages and limitations enounced above, prior art donor systems also employ a donor assembly which consumes valuable space within the volume defined by the sump thereby reducing the capacity thereof.

In prior art donor assemblies, doctor blades are required to insure that only a very uniform and predetermined amount of toner is carried by the donor roller or element to the developing brush. Besides the obvious drawback of cost, such doctor blades, once damaged or nicked, would fail in achieving uniformity of toner on the donor roller and hence create inconsistencies in the developed images. Damage could be the result of carrier beads or brush bristles being carried up by the donor roller or other contaminants getting into the system. These foreign elements in the donor assembly threatened not only to damage the doctor blade but also, more seriously, to damage the surface of the donor roller. This latter damage may extend along the entire circumference of the roller causing the applicator to have an excessive concentration of toner in a well defined area resulting in a consistent contrast deviation in the developed image. The cure for such a problem is replacement of the donor roller.

In mobile or unstable environments, the disorientation of the developer assembly causes undesirable shifts of developer in the donor assembly making uniform developing difficult since the developer may only be at one end of the donor assembly.

Also, certain solid types of donor assemblies also render the reloading of the sump difficult unless total accessibility to the sump is permitted.

It is, therefore, an object of the present invention to improve donor assemblies for toner conveyance to a developing member.

It is also an object of the present invention to provide improved donor assemblies which are efficient independent of additional apparatus for resituating developer in the sump.

Another object of the present invention is to provide an improved donor system wherein the effective capacity of the sump is maximized without altering the size thereof.

Yet another object of the present invention is to provide an improved donor assembly which can operate efficiently without carrier beads or doctor blades.

And a further object of the present invention is to provide an improved donor assembly which is insensitive to disorientation.

Another object of the present invention is to provide improved fibrous applicator developing systems wherein the donor assembly maintains the fibers of the applicator in a condition conducive to good development.

It is an object of the present invention to also provide an improved striking member which efiiciently fluffs a fibrous development applicator as well as uniformly distributes toner among the applicators fibers.

A still further object of the present invention is to provide a donor assembly which permits easy replenishment of the sump.

These and other objects which may become apparent are accomplished in accordance with the principles of the present invention wherein the donor assembly is comprised of a plurality of elongated members which define a volume at least partially occupying a sump of marking material through which these members are moved during operation. The donor members may be circular, crescentic, or other configurational crosssections and may or may not cooperate with a doctor blade. They may be in the form of taut flexible elements which are vibrated slightly to remove excessive toner. In certain embodiments, a striking element in the form of a thin taut but flexible wire or other material is used to charge and fluff the fibrous applicator as well as redistribute undesirable concentrations of toner within the applicator.

These objects and other features of the present invention may be appreciated and better understood upon reading the following detailed description in connection with the appended drawings wherein:

FIG. 1 is a cross-sectional view of one embodiment of the present invention showing the sump housing, donor and developing assemblies;

FIG. 2 is a cross-sectional view of an alternative embodiment of the present invention showing a detachable sump;

FIG. 3 is a cross-sectional view of another alternative embodiment of the donor assembly of the present invention;

FIG. 4 is a cross-sectional view of an alternative embodiment of the donor assembly.

FIG. 5 is a cross-sectional side view of another embodiment of the present invention showing the sump housing and donor assembly;

FIG. 6 is a cross-sectional view of one of the donor wires used in the embodiment of FIG. 5;

FIG. 7 is a front view of the embodiment of FIG. 5 with some parts broken away for clarity;

FIG. 8 is an illustration of a portion of another embodiment of a donor assembly of the present invention showing a vibrator different from that shown in FIG. 5;

FIG. 9 is an alternative embodiment of the donor assembly using non-parallel donor members; and,

FIG. 10 is an alternative embodiment of the present invention employing a striking element in accordance with the principles of the present invention.

Reference will now be made to FIG. 1 which illustrates in cross-section an embodiment of the present invention in the environment of an electrographic recorder. As is well known, in electrography discrete electrostatic charge patterns are placed on an insulative recording medium which are then rendered visible through appropriate developing techniques. Basically, any developing technique consists in bringing suitable marking particles into contact or close proximity with the latent pattern to be developed. These particles are then attracted and held by the pattern making it visible.

FIG. 1 illustrates one such developing technique in the form of a cylindrical applicator, such as natural fur brush 2, which is mounted for rotation about shaft 4. A support member 6 is spaced from shaft 4 so that as the brush rotates in the direction of the arrow a latent pattern-bearing recording medium 7 supported by member 6 will partially obstruct the bristles at that portion of the brush 2 adjacent thereto.

The developing brush 2 is isolated from the remaining areas of the apparatus in which it is incorporated by way of a shroud or housing 8 and a silicon rubber seal 10. The former may be supported by the machine side frame while the latter is supported along one edge of the sump housing designated by the reference numeral 12. The other edge of the sump housing has attached thereto a movable door 14 which is hinged to move about a shaft 16. Through this opened door 14, developer material may be loaded into the sump housing 12.

Within the sump housing is a donor assembly comprised essentially of four components. A basic shaft 18 is power driven to rotate the donor assembly in a direction indicated by the arrow and this shaft may be suitably fixed for rotation to a side frame of the apparatus in which the present invention is incorporated. It should be understood that this shaft 18 would then pass through one side panel of the sump housing 12.

Fixed to this shaft for rotation therewith is a flange member 20 which is positioned in and to one side of the sump housing. This flange member 20 has two support flanges 22 and 24 associated with it which extend therefrom in a direction substantially parallel to the axis of shaft 18. It may be apparent that support flanges 22 and 24 may be integral with flange member 20 such that components 20, 22 and 24 are actually one piece of material.

Attached to the outer surface of support flanges 22 and 24 or the surface remote from shaft 18 are two arcuate or crescentic members 26 and 28, respectively. Each of the elements 26 and 28 which will be referred to hereinafter as donor members have two edges substantially parallel to the axis of shaft 18 which are preferrably tapered as illustrated in FIG. 1. These edges may be identified as lead and trail edges depending on the direction of rotation of the donor assembly. As will be seen hereinafter, this facilitates passage of the donor member through the quantity of developer material 29 in the sump housing 12 as the shaft 18 is driven to rotation by a suitable source of motive power.

The center of curvature of the donor members 26 and 28 is not coincident with the axis of shaft 18 as these members are mounted as shown in FIG. 1. This feature is not critical although the curvature characteristic as illustrated is preferred since the rotation of donor members 26 and 28 will not tend to form a cavity in the material in the sump. In addition, by choosing a center of curvature different from the axis of shaft 18, the donor members as they rotate about shaft 18 agitate and disturb the developer material 29 in the sump more than if their center of curvature coincided with the axis of shaft 18. Furthermore, members 26 and 28 need not have a surface curvature consistent with a sin gle center of curvature.

The materials used may vary considerably. For example, components 20, 22, 24, 26 and 28 may be made of sheet metal with members 26 and 28 optionally having their exterior or convex surface coated with a suitable insulating material to assist in triboelectrically attracting toner particles from the sump as the donor assembly rotates therethrough. The housing 12 may be either suitably formed metal, plastic, or any other suitable insulator.

Although the embodiment of FIG. 1 is not presented in the drawings from a point of view lying on a line perpendicular with the axis of shaft 18, such a view is easily visualized when it is considered that the cylindrical brush 2 and its associated structures are substantially coextensive with the area or zone on the recording medium in which latent patterns are to be recorded during the recording process. Accordingly, the donor assembly is preferrably coextensive with the axial dimension of the brush 2. However, it may vary depending upon the actual effective length of the developer mechanism. The door 14 may have a dimension perpendicular to the plane of the drawing substantially equal to the dimension of the donor assembly or may have a somewhat shorter dimension. Of course, the sump housing 12 has a dimension parallel to the axis of shaft 18 slightly larger than the similar dimension of the donor members 26 and 28. Support flanges 22 and 24 may be substantially coextensive in this axial dimension with donor members 26 and 28 or may have a dimension only sufficient to provide adequate support to the donor members. Flange member 20 as shown in FIG. 1 would occupy a position on the far right side of the sump housing 12 as FIG. 1 is viewed from the right. The shaft 18 may extend through the sump housing to be fixed to or even pass through a similar support flange as flange 20 at the left extreme of the donor housing.

However, this is usually not necessary but may be providcd for additional support of the donor members 26 and 28. Members 22 and 26 and 24 and 28 may be at tached to each other in any suitable fashion such as rivoting, welding, etc. Also, while flanges 22 and 24 are described, donor members 26 and 28 may be integral with flange 20.

In operation the donor assembly and more specifically shaft 18 is driven to rotate in the direction indicated by the arrow moving successively donor members 26 and 28 in a clockwise direction as FIG. 1 is viewed through the developer material 29 in the sump housing 12. Because of the unique construction of the donor assembly, this developer material occupies not only the low points outside of the donor members but also occupies a portion of the volume defined by these donor members. This is made possible by the openings between the adjacent edges of the donor members 26 and 28. These openings allow developer material to freely enter and leave the volume defined by the donor assembly. Therefore, as the donor assembly rotates, for example, and donor member 28 moves to contact the fur brush 2, developer material within the donor assembly is permitted through gravity to egress from the donor assembly via the opening between the trail edge of donor member 28 and the lead edge of donor member 26 into the sump proper.

Similarly, as donor member 26 proceeds in a clockwise direction its lead edge directs developer material into the concavity formed by its interior surface and permits this developer material to flow back intothe sump as its trail edge passes the lowermost point of the sump. This action of the donor members 26 and 28 thereby agitates completely the material in the sump and permits developer material occupying portions of the volume defined by the donor members 26 and 28 to replenish the developer material in the sump itself. As is illustrated in FIG. 1, the clearance between donor member 28 and the lowermost portion of the sump housing 12 is very small. In this way substantially all of the developer material in the sump is fully utilized by contact exposure to the moving donor members.

As the donor members 26 and 28 move through the developer material into sump 12 toner particles adhere themselves to the exterior convex surface of the donor members and are carried on these members into contact with the bristles on brush 2. At this point, because of triboelectric attraction these toner particles are transferred and loaded onto the bristles of the developing brush 2. This brush which rotates in the same direction at the point of contact with the donor assembly then conveys these marking particles to the development zone defined by support 6 where these marking particles are transferred to the recording medium 7 to render visible latent patterns thereon.

Mounted on the housing 12 is a doctor blade assembly comprised of flange members 30 and 32 between which is supported a doctor blade member 34 made of any suitable resilient material, such as silicon rubber or plastic. As shown in FIG. 1, these flange members 30 and 32 are rotatably fixed to a support shaft 36 to permit the doctor blade 34 to move on the cam surface provided by donor members 26 and 28 as the donor assembly rotates in a clockwise direction. The function of the doctor blade is to meter at predetermined amount of toner adhering to the exterior surface of the donor members by removing excessive toner. This prevents non-uniform concentrations of toner being transferred to the fur brush 2 thereby creating variations in density of the developed electrostatic charge patterns. Also coupled and fixed for rotation with the doctor blade is a plurality of agitating fingers 38 which are uniformly spaced along the axis of support shaft 36 coextensive with the axial dimension of the donor assembly itself. As shown in phantom in FIG. 1, as the doctor blade is moved up and toward the fur brush, the fingers 38 are also moved up an equal amount. As the trail edge of a donor member leaves contact with the doctor blade, the doctor blade will fall into the space between donor members causing the agitating fingers 38 to also fall back against the interior surface of the sump housing 12. This effectively agitates any developer material which may, under certain environmental conditions, cake or build up on that side of the housing 12 as a result of the clockwise movement of the donor assembly.

It will be realized because of the structure of the donor assembly that developer mixture placed in the sump via the opening closed off by the door 14 will fall under force of gravity into the donor assembly and on one side thereof. The openings between the lead and trail edges of the donor members facilitates this loading. If these spaces were not available, a very limited amount of developer material could be added to the developer sump without overflowing through the opening associated with door 14.

Therefore, in accordance with the principles of the present invention, developer material may be loaded into the sump readily without moving the donor assembly itself. Furthermore, it can be seen that the type of structure of the donor assembly permits a maximization of the capacity of the sump for holding developer material and further acts to provide a cam surface upon which agitating fingers can be actuated in a very simple and inexpensive manner.

Reference will now be made to an alternative embodiment illustrated in cross-section in FIG. 2. As shown, a shaft 40 which may be fixed for rotation in the same manner as shaft 18 of FIG. 1 is attached to a support plate 42 of circular configuration This plate supports adjacent its periphery and parallel to its axis as well as the axis of shaft 40 a plurality of donor members 44. As illustrated, these members may be cylindrical elongated rods which have dimensions parallel to the axis of shaft 40 similar to the dimensions of the donor members 26 and 28 of FIG. 1. The number of these rods may vary depending upon the speed of rotation of the donor assembly as well as their own radius.

A doctor blade assembly 46 is illustrated as being attached to part of the shroud 48 isolating the fur brush 50 from the other parts of the apparatus in which this donor assembly is incorporated. Such an assembly may take the form of that used in the embodiment in FIG. 1.

The shroud 48 may have associated with it two fixed snap ears 52 and 54 on opposite edges which may accommodate and cooperate with two snap catch grooves 56 and 58, respectively, molded on the inside surfaces of a pliable, preferably plastic, sump housing 60. The ears 52 and 54 and grooves 56 and 58 have a dimension substantially equal to the dimension of the donor assembly of FIG. 1 in a direction parallel to the axis of shaft 18.

The sump housing 60 of FIG. 2 is removable from shroud 48 by way of a formed handle or lever portion 62. By depressing this handle away from the shroud 48, the ear 54 is disengaged from the groove 58 and the housing 60 drops free of the shroud 48 and the donor assembly.

Installation of the sump housing carrying a quantity of developer material 61 is accomplished by simply pushing the housing 60 toward the shroud 48 until the ears and grooves engage permitting the donor assembly to be immersed into the developer mixture in the sump housing. This housing may be shipped or stored with a removable paper or cardboard lid mounted inside the housing keeping the toner or developer material from spilling from the housing.

Not illustrated in FIG. 2, of course, are the side panels of the housing 60 which are integral with the housing and formed of the same material such as plastic or other pliable material.

The donor assembly in the embodiment of FIG. 2 operates in a manner very similar to that of the donor assembly illustrated in FIG. 1. As shaft 40 is driven from a suitable source of motive power, the donor members or elements 44 move in a clockwise direction as illustrated by the arrow into the sump of developer material thereby attracting to the surface of each of the donor members toner particles for conveyance to the developing brush 50.

A pliable doctor blade assembly 46 mounted on shroud 48 acts to contact the donative surfaces of the donor members to meter a uniform layer of toneron this surface of each of the members 44.

The same novel features as set out in connection with the embodiment of FIG. 1 are also present in the embodiment of FIG. 2 in that the donor members define a substantially cylindrical open volume in which developer material may be situated during operation of the donor assembly. In addition, as the donor assembly rotates it agitates and resituates the developer material in the sump to utilize completely that material. The clearance between the lowermost portion of the sump housing 60 and the path defined by the movement of the donor members is very close so that substantially all the developer mixture will reach the donor members during the operation of the donor assembly.

It may be noted that the donor members or rods 44 need not necessarily be of a circular cross-section and may be crescentic having their concave surface facing toward shaft 40 or may be simple solid members having semicircular cross-sections with the flat sides thereof facing the shaft 40.

FIG. 3 illustrates another embodiment of the present invention wherein donor members 64 are driven through developer material 65 in a sump housing 66 via two drive gears 68 and 70 having about their periphery gear teeth 72. The donor members 64 may be circular cross-sectioned elongated rods as are illustrated in FIG. 2 coupled together by a flexible connecting or linking structure having links 74 between each donor member 64.

The links may be of any suitable material such as plastic segments molded with rods or donor members 64, or even a single loop attached to each member 64.

The drive gears 70 and 68 are driven by shafts 75 in a direction indicated by the arrows to bring donor members past a doctor blade assembly 76 and into toner transfer relation with a developing brush 78. As shown, the pitch of the teeth 72 on the drive gears are such as to accommodate the spacing between adjacent donor members 64 to provide a driving surface for the chain of donor members. Doctor blade type assembly 76 is provided also adjacent wheel 70 to further isolate toner clouds from other parts of the apparatus.

An additional baffle member may be provided intermediate the drive gears 68 and 70 to prevent toner clouds or spillage from the sump toward the brush 78 in case of disorientation of the donor assembly. The baffle 80 may be supported from the sides of the sump housing 66 which are not illustrated in FIG. 3 or on the shafts 75 supporting wheels 68 and 70.

Each of the illustrated drive wheels 68 and 70 has a counterpart mounted on the same shaft and adjacent the other side of the sump housing to maintain the donor members in parallel and to provide uniform driving force on the donor member chain.

The dimension of the donor members in the direction perpendicular to the plane of the drawing may be the same as the dimensions described for the donor members in FIGS. 1 and 2.

In operation, drive wheel 68 acts to pull the donor members into the sump material 65 when the sump housing is at full capacity thereby causing toner adherence to the surface of the donor members 64. When the developer material in the sump is gradually consumed, the larger segment of the donor member chain lays upon and is drawn across the remaining developer material. This continues until the chain of donor members is almost contacting the bottom of the sump housing. The length of this chain is selected to accomplish this result taking into consideration the spacing between ggve wheels 68 and 70 as well as the size of the housing As shown in FIG. 3, the chain of donor members 64 is placed initially about drive wheels 68 and 70 to insure the requisite tautness in the area of contact with the developing brush 78.

As was the case with the donor members in the embodiment of FIG. 2, members 64 may take different configurations and still perform in accordance with the principles of the present invention.

Reference will now be made to FIG. 4 which illustrates a donor assembly similar to a certain extent to the embodiment of FIG. 2 as well as FIG. 1 wherein crescentic members 81 are positioned about a shaft 82 and fixed to rotate therewith by way of their coupling to or being integral with flange member 84 which is attached to the shaft 82. The furthest outer extremity of each of the donor members 81 relative to the axis of shaft 82 form a right cylinder by revolution when the assembly is rotated. The individual centers of curvature of the exterior surface of the donor members 81 do not coincide with the axis of shaft 82. This augments the agitative effect of the donor members when they pass through the sump of developer material. In fact the radius of curvature of the exterior surfaces in greater than the radius of curvature of interior surfaces.

FIGS. and 7 illustrate another embodiment of the present invention incorporating some features not disclosed in earlier embodiments. FIG. 5 is a crosssectional view taken along lines 5-5 in FIG. 7 while FIG. 7 represents a front view of the donor assembly with part of the housing, brush, and other portions broken away. In these Figures there is illustrated a sump housing 86 which defines a sump cavity or reservoir adapted to contain a quantity 85 (not shown in FIG. 7) of electroscopic marking particles.

It is noted that the embodiments illustrated in FIGS. 5, 7, 8, 9, and are practical and efficient in using only toner in the sump without the usual addition of carry beads.

Mounted at the extremities of a shaft 88 for rotation therewith are located support discs 90 between which are tautly suspended a plurality of very thin, flexible donor members 92. The shaft 88 is mounted for rotation on suitable bearing surfaces 94 in the side walls of the housing 86 as shown best in FIG. 7. Also supported on shaft 88 are a plurality of thin baffle discs 96 which are held in spaced apart relationship on the shaft and from the support discs 90 by spacer sleeves 98.

Both the baffle discs and the sleeves are dimensioned to fit loosely upon shaft 88 in such a manner as to not readily rotate with this shaft. As a further impediment to the rotation of the baffle discs 96 with the shaft 88, a holding shaft 100 is used which passes through the portion of the baffle discs closest to the low portion of the sump housing 86. This shaft may be fixed permanently to the respective baffle discs or may just be secured to one baffle to prevent its dislodging itself from any of the extreme baffle discs.

The effect of holding shaft 100 is to weight the baffle discs so that thay remain stationary while shaft 88 rotates. In addition, the toner in the sump housing also affords greater resistance against this holding shaft than against the thin baffle discs. This increased resistance further impedes rotation of these discs with shaft 88. As best shown in FIG. 5, each baffle disc would normally have a substantially circular configuration and conform as close as possible to the interior surface of the sump housing 86. However, at that point closest to the developing applicator 102, shown as a fibrous member, the area of a chord has been removed from the circle. This serves to maintain a spacing between the baffle discs and the applicator 102 as the latter rotates. Contact between the baffle discs and the brush or applicator 102 is to be avoided since these baffle discs may attract toner from the applicator 102 prior to delivery of this toner to the development zone or else add excessive toner to the applicator.

Only by way of example, certain dimensions have been used successfully in this embodiment and are stated without any intention that this embodiment be limited to these parameters. Depending upon the axial dimension of shaft 88 the baffles may be spaced approximately 075 inches from each other and may be made of aluminum approximately 0.020 inches in thickness so as to occupy as little space in the sump housing as possible.

The donor members 92 may be made of any suitable material either conductive or insulative. Conductive wires 0.006 inches in diameter have been successfully employed. The degree of tautness which these donor members experience does not have to be great but only sufficient so as not to sag or have slack at the time they contact the bristles of the applicator 102.

As may be expected from the earlier description of the previous embodiments, as the support discs rotate in the direction of the arrow shown in FIG. 5 they travel in a generally circular path through a quantity of toner confined in the sump housing 86 and attract and hold a certain quantity of this toner as they egress from the sump.

FIG. 6 illustrates what is believed to be the approximate toner accumulation on any one of the donor members 92. The arrow in FIG. 6 indicates the direction of movement of the donor member 92 both in the sump and outside the sump. As shown, a large quantity of toner builds up on the leading surface of the donor member while the remaining surface of this member retains a substantially uniform layer of toner. As noted hereinabove, the large amount of toner on the leading surface of the donor member is undesirable and contributes to an inconsistent developed image and it is therefore necessary to remove this excessive amount of toner. In prior situations as well as in certain other embodiments of the present invention a doctor blade has served this function.

Because of the resilient characteristics of donor members 92 a doctor blade is not necessary for the removal of this excessive toner. This function can now be performed by a simple resilient member 104 which may comprise a piece of metal wire, for example, 0.012 inches in diameter. A loop may be formed in the wire as shown best in FIG. 5 to prevent any fatiguing problems and one end of the wire may be mounted in housing 86 by way of an appropriate mounting element 105. It should be understood that this element 104 may be made of other materials rather than metal such as rubber or plastic. The effect of this member 104 when it contacts a donor member 92 as the support discs rotate is to slightly deflect the donor member and then release it. This mechanical action may be compared to the picking of a guitar string. The results of this flicking of the donor member is to jar the excessive toner from the donor member 92.

It is speculated that the success of this flicking action is due to the fact that the excessive toner is attracted to adjacent toner in the excessive quantity on the donor member 92 to a lesser degree than a uniform toner layer adhering directly to the surface of the donor member 92. Consequently, the plucking action of the flicker member 104 is such as to dislodge all the toner carried by the donor member except for a uniform llll layer held directly by the surface of the donor member itself. That toner which is flicked off is permitted to fall back into the sump. In this manner uniform amounts of toner are systematically and consistently supplied to the attractive influence of the applicator 102 through mutual contact therewith.

Because of the possibility of generating a large powder cloud of toner at the region of contact between the flicker member 104 and the donor member 92, a protective hood 106 is mounted on housing 86 to extend transverse to shaft 88 and coextensive with this region. This element is optional and is used as an isolating feature between the donor assembly and other portions of the apparatus in which the present invention may be incorporated.

From the view afforded by FIG. 7 it may be appreciated that the baffle discs 96 create partial compartments along the axial dimension of the sump housing 86 in which quantities of toner may reside until consumed during the operation of the donor assembly. This is particularly useful in mobile enviroments when the chance that the sump housing may be disoriented from the horizontal is very great. If this occurs, such as tilting the structure as illustrated in FIG. 7 30 with the horizontal (horizontal being from left to right as the Figure is viewed) the toner between baffle discs 96 will be shifted against an adjacent baffle disc thereby preventing all or a large portion of the toner from shifting from one side of the sump housing all the way to the other side. Because of the fine profile of the donor members 92 the clearance of these members between the bottom of the sump housing 86 and the lower edge of the baffle discs 96 may be very small. This further makes possible the isolation of toner in adjacent compartments formed by the baffle discs since the toner in such a small clearance will form a block and not permit more toner to pass beneath the baffle discs 96.

To further prevent large scale shifting of the toner from one extreme of the sump housing to the other and to assist the baffle discs, the housing 86 may be provided with additional baffle plates 108 mounted thereon.

These baffle plates are seen on the left side of the shaft 88 in FIG. and seen best in FIG. 7 at that portion of the drawing wherein the applicator I02 and some of the baffle discs 96 are broken away. From the latter figure it may be noticed that these baffle plates 108 are located along an interior side of the sump housing 86 is alignment with baffle discs 96 mounted on shaft 88. Not seen in FIG. 7 but illustrated in FIG. 5 are another set of baffle plates 109 which are located on the right side of shaft 88 and mounted in a similar fashion as baffle plates 108 to the side of sump housing 86. These baffle plates 109 are also in alignment with the baffle discs 96.

The combined effect of the baffle discs 96 and baffle plates 108 and 1109 is to divide the volume of the sump housing into individual compartments to effectively prevent large scale shifting of toner in the sump housing when this housing is disoriented relative to the horizontal.

Reference will now be made to FIG. 8 which illustrates alternative apparatus for removing excess toner from the donor members 92. Elements identical with elements in FIGS. 5 and 7 are identified by the same reference numerals.

In place of the support discs there may be provided resilient support arms which extend radially from a hub ll2 fixed on shaft 88 to rotate therewith. At the nonsupported end of each support arm there may be a mounting arrangement for supporting one end of the thin donor member 92. The support arms A resilient member 114 is held in obstructing relationship with each of the support arms 110 by the sides of the sump housing 86. As the support arms move into contact with the flicking member 114 they are slightly deflected and then released having the same affect on the excess toner on the donor member 92 as element JIM had in the embodiments of FIGS. 5 and 7.

In view of this disclosure it may be apparent that there may exist alternative methods of vibrating the donor member 92 to achieve uniform toner distribution on this member. For example, a small impact hammer may be timely actuated to gently tap each donor member 92 as it emerges from the sump of toner.

FIG. 9 represents an alternative method of allocating donor members between support discs 90. In this figure a single piece of thin wire or other suitable material 116 is threaded back and forth between the two support discs 98 to form, as shown in FIG. 9, six taut segments or effective donor members. Each one of the donor members 116 forms an angle different than ninety degrees with the plane of either support disc 90. It is apparent, of course, that single pieces of wire or material may be used for each length of donor member shown in FIG. 9.

An advantage of the structure of FIG. 9 is that the donor members contact the bristles or fibers of applicator 182 at the point of toner transfer thereto at different angles each time there is contact. This promotes a fluffy and noncompacted applicator fiber which some times occurs when a donor member such as a solid cylindrical device is used. Since the brush or applicator 102 does not become compacted or formed in one direction better development is possible. Furthermore, toner is not permitted to build up on the side of the fiber remote from the donor member at point of contact but is dislocated from this position by the different angle of impact on each succeeding donor member.

FIG. 10 illustrates another embodiment of the present invention which is very similar to the view of the embodiment illustrated in FIG. 5 wherein similar elements are referenced by like numerals. The structure illustrated in FIG. 18, however, differs from that of FIG. 5 in the omission of flicking of vibrating member 104 and the addition of a striking element 118 in the form of a thin flexible wire-like structure. This striking element may be a metallic wire, or other material, such as plastic, of approximately 0.012 inches in diameter and may be tautly suspended between the sidewalls of the sump housing 86 clear of the rotation of the support discs 90.

The effect of the striking member is threefold. It serves to triboelectrically charge the fibers of applicator 102 so as to make it more attractive to toner particles. In addition, its position within the effective perimeter of the applicator which may be compacted after developing contact with a recording medium. And finally, but not of any less importance, the striking element serves to redistribute excessive concentrations of toner throughout that portion of the applicator most proximate to it.

It will be noted that the structure of FIG. does not include vibrator element 104 as did the structure of FIG. 5. Therefore, as a result of this omission the donor elements 92 egress from the toner sump bearing amounts of toner as represented generally by the illustration of FIG. 6. This excessive amount of toner on the leading surface of the donor element is undesirable if permitted to be transferred to the developing applicator 102 without any other steps being taken to make this toner concentration more uniform. If nothing else is done, therefore, these excessive toner concentrations will be reflected in variations of contrast in the developed image on the recording medium. However, the action of the striking element 118 is such as to dislocate this excessive toner clinging to fibers of the applicator to form a powder cloud of this excessive toner. This formation of a cloud of toner within the fibers of the applicator in conjunction with the triboelectric charging of the fibers by striking element 118 cooperate to redistribute that toner which is in excess on certain fibers to fibers which can attract and hold more toner. This in effect takes excessive toner from fibers holding too much toner and divides this amount of toner among fibers which can hold more toner. As noted before, the toner being held on toner is more weakly held by the fiber than toner contact the fiber itself.

The thin flexible nature of the striking wire or element 118 is believed to play an important role in the efficiency and effectiveness of the donor assembly and developing applicator. To replace the striking wire 118 with, for example, a blade or planar member would not have the same result as that achieved by a wire-like structure. For instance, a striking plate or blade, or other large area structure such as a comb-like member, will attract and build up excessive amounts of toner resulting in poor operation of the developer applicator. In such instances, such structures may take toner unevenly from the applicator, causing variation in the developed image. Furthermore, in other instances large amounts of accumulated toner may fall onto or be picked up by the applicator to also cause variation in development or to be dislocated from the applicator during its revolutions to contaminate other areas of the apparatus. The thin structure of the striking wire 118 is such that it will build up only a very small and predetermined amount of toner and therefore will not accept any more build-up. In addition, the flexibility of the striking member 118 further insures no excessive buildup as well as contributes further to the dislocation of excessive toner concentrations in the fibers of applicator 102. by its vibratory action as the fibers and the striking member mutually deflect upon conact.

It should be noted that the embodiment of FIGS. 5,7, and 9, as well as FIG. 10, may very well operate without the flicking element 104 or striking member 118, in the case of FIG. 10, if slight variations in toner concentrations in the applicator can be tolerated. This is made possible by the flexible nature of the thin donor members 92 and 116. The contact of the applicators fibers with the donor member itself is sufficient to vibrate the donor member thus dislocating excessive amounts of toner therefrom. It is believed that while some of the dislocated t'oner is thrown into the applicator some falls back into the sump housing.

In summary therefore, objects of the present invention are achieved by the movement of successive, discrete elongated donor members through a substantially identical closed path which defines a dimension of a volume at least a portion of which is within a sump housing. This housing supports a quantity of marking particles, i.e., toner with or without carrier particles, within the defined volume.

The other dimension of the volume so defined is equal to the elongated dimension of the donor members. Since this volume is open as contrasted with being solid or completely occupied with a solid integral member, marking particles may readily pass into and out of the volume.

The action of the donor members in transferring marking particles to the developing applicator, such as the fur brush, is such as to supply such particles in a uniform manner to the applicator. This is possible in spite of the physical discontinuity of the donative surfaces of the donor assembly. This is due to the relative velocities of the developing applicator and the donor assembly. Preferrably, the relative velocity ratio of the applicators surface and the surface of a single donor member at the point of mutual contact is approximately ten to one. For example, in the embodiment of FIG. 1, the donor assembly can be driven at speeds from four to forty revolutions per minute while the brush may rotate from forty to four hundred revolutions per minute. Therefore, the periphery of the brush may make one complete revolution and receive marking particles from a single donor member.

These relative velocities are readily implemented by utilizing a single source of motive power and a conventional speed reducing gear arrangement to couple the slower rotating shaft to the motor or motive power source which could drive the faster shaft directly.

Donor members flexible enough to be vibrated or deflected with slight force may be used without a doctor blade and in the presence of a pure toner sump. A wirelike striking member may also be used to triboelectrically charge and fluff the fibrous applicator as well as redistribute excessive amounts of toner in the applicator. Baffles in the sump act to prevent or minimize large scale toner shifts normally expected when the donor assembly becomes disoriented with respect to the horizontal.

While the present invention has been described with particular structures in specific embodiments other modifications and equivalents may suggest themselves without departing from the inventive concepts of the present invention.

For instance, the doctor blade assembly of'FIGS. l and 2 may easily be substituted for the metering arrangement in the embodiment of FIG. 3 and vice versa. Furthermore, the sump housing of FIG. 2 may be used equally well with the other embodiments.

The donor assembly of the present invention may be used with electroscopic marking particles as well as magnetic marking particles.

It may be apparent from this disclosure that any combination of the various donor members described hereinabove in connection with FIGS. 1 to 4 may be used effectively in a donor assembly. For example, one of the crescentic donor members of FIG. 1 may be superseded by one or more of the rod-like donor member structures illustrated in FIG. 2. Any such modification or derivatives are within the scope of the present invention.

In addition, donor members having an oval or elliptical cross-section may also be employed in the embodiments of the present invention.

Although the present invention has been described in a system for developing latent images deposited on a medium through electrography, it is itself not limited to any particular application. As may be appreciated, the present invention is also suitable in optical xerographic and magnetic recording systems.

The number of donor members to be mounted on support discs 90 in the embodiment of FIGS. to may vary as a function of the desired amount of toner to be supplied to the applicator 102. This, as in the embodiments of FIGS. l to 4, also depends on the relative rotation rates involved and the size of the applicator 102.

Striking element 118 may be useful when the number of wire-like donor members is very low. This is due to the fact that if large numbers of donor members are used, they themselves sufficiently fluff and charge the applicators fibers as the donor assembly is rotated.

While the use of striking element 118 has been described in connection with a particular donor assembly, it also has utility in any fibrous applicator development system regardless of the donor assembly design.

The flicking or vibrating element has been described as being located at one side of the sump housing even though it may be located at the other points along shaft 88. Of course, more than one such element may also be employed.

It should be understood that while the donor elements in the embodiments disclosed herein may be conductive they may also be conductive with an insulative sleeve or layer coextensive with their exterior or toner bearing surfaces.

Furthermore, while the embodiments of FIGS. 5 and 7 to 10 have been described using wire-like conductors or insulators having diameters of 0.006 and 0.012 inches, elements having diameters around 0.003 inches to one 30 second of an inch may also be used. The term wire-like" is intended to include this range of diameters as well as other diameters as long as the element is flexible in the context of the present invention.

Therefore, while the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention.

What is claimed is:

1. A developing system for latent patterns employing electroscopic marking particles comprising:

a cylindrically shaped applicator adapted to be rotated about an axis and capable of holding electroscopic marking particles;

a plurality of elongated donor members each having a surface portion capable of attracting electroscopic marking particles;

support means for supporting each of said donor members substantially in spaced parallel relation with each other;

means coupled to said support means for moving said donor members through a closed path, a portion of which brings said donor members successively into contact with said applicator;

a shroud partially enclosing said applicator at least along its axial dimensions and having engageable areas thereon; and

a housing resiliently engaged with said areas on said shroud and adapted to support a quantity of electroscopic marking particles adjacent said closed path, said housing being detachable from said shroud by moving said housing from said areas.

2. The combination recited in claim 1 wherein said shroud is made of metal and said housing is made of plastic.

3. The combination recited in claim 1 wherein said engageable surfaces comprise outwardly extending flanges for interfitting with grooves in said housing.

4. A developing system for latent patterns employing electroscopic marking particles comprising:

a cylindrically shaped applicator adapted to be rotated about an axis and capable of holding electroscopic marking particles;

a plurality of elongated donor members each having a surface portion capable of attracting electroscopic marking particles, at least one of said donor members having a crescentric cross-section;

support means for supporting all of said donor members substantially in spaced parallel relation with each other with openings between adjacent members; and

means coupled to said support means for moving said donor members through a closed path, a portion of which brings said donor members successively into contact with said applicator;

5. The combination recited in claim 4 wherein said donor members jointly define an open volume into which said toner particles move. 

1. A developing system for latent patterns employing electroscopic marking particles comprising: a cylindrically shaped applicator adapted to be rotated about an axis and capable of holding electroscopic marking particles; a plurality of elongated donor members each having a surface portion capable of attracting electroscopic marking particles; support means for supporting each of said donor members substantially in spaced parallel relation with each other; means coupled to said support means for moving said donor members through a closed path, a portion of which brings said donor members successively into contact with said applicator; a shroud partially enclosing said applicator at least along its axial dimensions and having engageable areas thereon; and a housing resiliently engaged with said areas on said shroud and adapted to support a quantity of electroscopic marking particles adjacent said closed path, said housing being detachable from said shroud by moving said housing from said areas.
 2. The combination recited in claim 1 wherein said shroud is made of metal and said housing is made of plastic.
 3. The combination recited in claim 1 wherein said engageable surfaces comprise outwardly extending flanges for interfitting with grooves in said housing.
 4. A developing system for latent patterns employing electroscopic marking particles comprising: a cylindrically shaped applicator adapted to be rotated about an axis and capable of holding electroscopic marking particles; a plurality of elongated donor members each having a surface portion capable of attracting electroscopic marking particles, at least one of said donor members having a crescentric cross-section; support means for supporting all of said donor members substantially in spaced parallel relation with each other with openings between adjacent members; and means coupled to said support means for moving said donor members through a closed path, a portion of which brings said donor members successively into contact with said applicator;
 5. The combination recited in claim 4 wherein said donor members jointly define an open volume into which said toner particles move. 